MX2015000822A

MX2015000822A - Method for continuous production of foams in tubes.

Info

Publication number: MX2015000822A
Application number: MX2015000822A
Authority: MX
Inventors: Christof Grieser-Schmitz; Carsten Ellersiek
Original assignee: Basf Se
Priority date: 2012-07-17
Filing date: 2013-07-15
Publication date: 2015-08-12
Also published as: DK2874808T3; CA2879364A1; PL2874808T3; RU2632689C2; KR20150036660A; BR112015000974A2; EP2874808B1; RU2632689C9; CN104684722A; KR102123921B1; EP2874808A1; JP2015530939A; CN104684722B; AU2013292168A1; JP6193372B2; RU2015105054A; WO2014012877A1

Abstract

The present invention relates to a continuous method for the production of an insulated tube comprising at least one medium tube, a shell tube, a layer of at least one polyurethane between the at least one medium tube and shell tube and a film sleeving between the at least one polyurethane and the shell tube, comprising at least the steps (A) providing at least one medium tube and one film sleeving continuously formed from a film in a gripper-belt, wherein the at least one medium tube is arranged inside the film sleeving in such a manner that between the at least one medium tube and film sleeving a gap is formed, (B) charging a polyurethane system comprising at least one isocyanate component (a) and at least one polyol (b) into the gap, (C) foaming and curing the polyurethane system, and (D) applying a layer of at least one material to the film sleeving in order to form the shell tube, wherein the polyurethane system has thixotropic properties.

Description

i PROCESS FOR THE CONTINUOUS PRODUCTION OF FOAMS IN TUBES Description The present invention relates to a continuous process for producing an insulated tube comprising at least one middle tube, an outer tube, a layer of at least one polyurethane between at least one middle tube and outer tube and a film tube between at least one a polyurethane and the outer tube, comprising at least the steps (A) provision, in a jaw band, of at least one middle tube and a tube of film formed continuously from a film, where at least one tube medium is disposed within the film tube in such a way that a separation is formed between at least one middle tube and the film tube, (B) introduction of a polyurethane system comprising at least one isocyanate component (a) and at least a polyol (b) in the separation, (C) produce foam and allow the curing of the polyurethane system and (D) application of a layer of at least one material to the film tube to form the outer tube, where the polyurethane system has propied thixotropic ades.

Tubes isolated by means of polyurethane foams are known in the art and are described, for example, in EP 1 141 613 B1, EP A 865 893, EP 1 777 051 B1, EP 1 595 904 A2, WO 00 / 39497, WO 01/18087 A1, EP 2 143 539 A1 and EP 1 428 848 B1. Isolated pipe systems are assembled from individual pipe segments. The lengths of the 6 m, 12 m and 16 m tubes are normally used for this purpose. The transition lengths required are specially manufactured or cut to size from existing prefabricated goods. The segments of individual tubes are welded together and are further insulated in the region of the weld using the existing sleeve technology. These sleeve connections cause greater potential damage than the tubes themselves. This difference results from the fact that the tube lengths are produced under fixed controllable conditions, in the production facilities. Sleeve connections often occur under time pressure in all types of weather at the construction site. Influences such as temperature, fouling and humidity often influence the quality of the sleeve connections. In addition, the number of sleeve connections represents a large cost factor in the installation of piping systems.

It is therefore desirable in the tube processing industry to install as few sleeve connections as possible, based on the length of a line. This is achieved through the use of longer individual pipe segments, although the production of these involves more demanding requirements and often leads to technical problems.

The majority of the individual tubes is produced by the discontinuous production of tube tubes. In this process, the middle tube, in a steel tube in general, is provided with star-shaped spacers that serve to center the inner tube. The medium tube is pushed into the outer tube, usually a polyethylene tube, so that an annular gap is formed between the two tubes This annular separation is filled with polyurethane foam, since it has excellent insulating properties. For this purpose, the slightly inclined double tube is provided with closure caps which are equipped with static ventilation holes. The liquid reaction mixture is subsequently introduced into the annular gap by means of a polyurethane measuring machine and flows downwardly still in liquid form in the annular gap until the reaction begins. From this point on in the time onwards, another distribution is produced by the flow of the foam whose viscosity increases slowly, until the material has reacted completely.

EP 1 552 915 A2 discloses a process for producing insulated tubes, in which a polyurethane system comprising an isocyanate component and a polyol component having a low viscosity of less than 3000 mPas is introduced into the separation annular formed by the middle tube and the outer tube. After the introduction, the polyurethane system produces foam and heals at the same time EP 1 783 152 A2 also discloses a process for producing insulated tubes, in which a polyurethane system comprising an isocyanate component and a polyol component having a low viscosity particularly less than 1300 mPas which is introduced in the separation annular formed by the middle tube and the outer tube The documents EP 1552915 A2 and EP 1783152A2 in Consequently, they describe processes for producing insulated tubes, in which the problem of complete filling of the tube before the production of foam and curing is solved by the use of polyol components having a particularly low viscosity and therefore good fluidity. Although these processes are suitable for producing insulated tubes having diameters greater than 355 mm and / or high density of foam, they show typical drawbacks of the batch process, for example, labor intensive and expensive manufacture and relatively thick cellular structure . In addition, tubes manufactured in a discontinuous manner have a relatively thick outer wall, since they have to withstand the internal pressure generated during the production of foam. This causes an increased, undesirable use of raw material and therefore an increase in manufacturing costs.

In addition, a uniform distribution of foam density is important for the quality of the tubes. However, this is not advantageous when the processes known from the prior art are used. Generally, a lower foam density is obtained at the ends of the tube and a higher density of foam is obtained in the medium. The longer the tube, the higher the foam density required of the foam in the annular separation due to production reasons.

A disadvantage of the continuous process known from the prior art is that large quantities of the polyurethane precursor mixture have to be introduced continuously into a tube. double in movement formed by a middle tube and external tube formed by joining an elongated film. Because this mixture can sometimes not be transported out fast enough, the foam can run out of the pipe in the front.

In addition, the continuous processes known from the prior art to date have not advantageously made it possible to produce insulated tubes having a pipe diameter greater than 355 mm. In the production of insulated tubes having pipe diameters greater than 355 mm using the processes known from the prior art, a large amount of polyurethane system has to be introduced into the film. Due to the low viscosity of the polyurethane systems which are generally used, the polyurethane precursor mixture can, in the prior art processes, drip from the tube formed in the front part and therefore is no longer available for the Real production of insulated tubes.

A further problem is to produce insulated tubes having high foam densities of the polyurethane foam by means of prior art processes. To achieve high foam densities, it is necessary to introduce a corresponding large amount of polyurethane system into the tube formed from a film. Here too, the introduced polyurethane system can run out of the tube in the front and therefore is no longer available for the actual process. High foam densities are required for tubes that are used under water and do not have to withstand the respective hydrostatic pressure.

It is currently difficult to produce insulated tubes having two or more tubes for a medium and having a homogeneous foam structure throughout the cross section of the pipe by means of the continuous processes of the previous technique. The reason for this is, for example, the different path length of the ascending foam when two tubes for a medium are introduced during production.

It was an object of the present invention to provide a continuous process for producing insulated pipes, providing pipes showing a foam density uniformly distributed over the length of the pipe and a homogeneous foam structure over the cross section of the pipe, and also a small cell diameter of the obtained polyurethane foam and thus a low thermal conductivity. It is a further object of the present invention to provide a process that ensures that the introduced polyurethane system does not run out on one side of the formed tube but remains completely in the gap between at least one middle tube and the film tube. It should also be possible to produce insulated tubes having large diameters and / or high foam densities of the insulating material in continuous form.

These objects are achieved according to the invention by a continuous process to produce an insulated tube comprising at least one middle tube, an outer tube, a layer of at least one polyurethane between at least one middle tube and outer tube and a tube of film between at least one polyurethane and the outer tube, comprising at least the steps: (A) Provision, in a jaw band, of at least one middle tube and one tube of film formed continuously from a film, wherein at least one middle tube is disposed within the tube of film in such a way that it is forms a separation between at least one middle tube and the film tube, (B) introduction of a polyurethane system comprising at least one isocyanate component (a) and at least one polyol (b) in the separation, (C) produce foam and allow the curing of the polyurethane system and (D) application of a layer of at least one material to the film tube to form the outer tube, where the polyurethane system has thixotropic properties.

The process of the invention is carried out continuously. This means, in particular, that each individual process step is carried out continuously.

The individual steps of the process of the invention will be described in detail below.

Stage (A): The step (A) of the process of the invention comprises the provision, in a jaw band, of at least one middle tube and a tube of film formed continuously from a film, where at least one middle tube is disposed within of the film tube in such a way that a gap is formed between at least one middle tube and the film tube.

According to the invention, at least one medium tube, preferably one, two, three or four tube / s for a medium are present. According to the invention, particular preference is given to one or two tubes / s for a medium, two tubes for a medium being very particularly preferably present.

At least one middle tube, which according to the invention has a diameter smaller than the film tube and which the outer tube formed in step (D) of the process of the invention, is arranged inside the outer tube in such a way that a separation is formed between the middle tube and the outer tube. The polyurethane system is introduced into this separation in step (B) according to the invention. Depending on the number of tubes for a medium that are present according to the invention, the formed separation has several forms. In the particularly preferred case where a medium tube is present according to the invention, an annular gap is formed. In the preferred embodiment in which two tubes are present for a medium according to the invention, a double annular gap is formed.

At least one medium tube used according to the invention is generally a steel tube having an external diameter of, for example, from 1 to 70 cm, preferably from 4 to 70 cm, particularly preferably from 10 to 70 cm and very particularly preferably from 20 to 70 cm. If more than one medium tube is present, these tubes may have identical or different external diameters.

Preference is given to all tubes for the medium present that have the same diameter. The length of at least one middle tube is, for example, 3 to 24 m, preferably 6 to 16 m. More preferably, at least one middle tube is produced as a rolled product having a length of, for example, 50 to 1500 m.

In the continuous implementation of the process of the invention, at least one medium tube is provided, for example, in the form of a rolled product. At least one middle tube can also be provided as straight tube lengths.

In step (A) of the process of the invention, at least one middle tube and a film tube formed continuously from a film are provided in a jaw band.

For this purpose, an elongated film is continuously removed from a roll and optionally joined by methods known to those skilled in the art, eg, soldier, to form a film tube. This connection, in a preferred embodiment of the process of the invention, is carried out in the jaw band in which at least one middle tube is also continuously fed. The film is preferably fed through a molded projection or film projection. It is preferably provided to a circular film tube that is formed.

The film may comprise at least one layer of thermoplastic polymer that preferably has a diffusion inhibitory effect with respect to cell and oxygen gases. The film preferably additionally comprises at least one layer of metal, for example aluminum. Films that are suitable according to the invention are known from EP 0 960 723.

The film used according to the invention preferably has a width that allows the formation of a corresponding film tube having an internal diameter in general from 6 to 90 cm, preferably from 12 to 90 cm, particularly preferably from 19 to 90 cm, very particularly preferably from 35 to 90 cm. this film is preferably provided as a rolled product.

The film used according to the invention can be made of any material that appears to be appropriate for the person skilled in the art, for example polyethylene.

The film used according to the invention in general has any thickness that seems to be appropriate for the person skilled in the art, for example from 5 to 150 pm.

A jaw band used according to the invention is known per se by those skilled in the art. It generally comprises two circumferential flanges which, depending on the dimensions of the tube, carry aluminum jaws that impart shape. These aluminum clamps are, for example, tube half-shells which, when joined, form the cross-section of the entire tube. Up to 180, for example, individual segments are installed in each circumferential flange.

At least one medium tube, in step (A) of the process of the invention, is disposed within the film tube in such a way that a gap is formed, in the case where a middle tube is present, an annular gap, between at least one middle tube and the film tube.

Particular preference is given to a middle tube which is disposed centrally in the preferably circular film tube to form a concentric annular gap. In the case where more than one medium tube is present, these tubes are preferably arranged symmetrically in the film tube.

Stage (B): Step (B) of the process of the invention comprises introducing a polyurethane system comprising at least one isocyanate component (a) and at least one polyol (b) in the separation, preferably in the annular separation.

The introduction according to step (B) of the process of the invention can, in general, be carried out using any apparatus known to those skilled in the art, for example high pressure metering machines which are freely available in the market, for example from the companies Hennecke GmbH, Cannon Deutschland GmbH or Krauss Maffei Kunststofftechnik GmbH. According to the invention, it is also possible to use a multiple nozzle bent so as to correspond to the radius of the separation formed for the introduction of the polyurethane system according to step (B) of the process of the invention.

In step (B) of the process of the invention, a polyurethane system having thixotropic properties is presented. The terms "thixotropy" and "thixotropic properties" are known per se to those skilled in the art. For the purposes of the invention, Thixotropic properties means that the liquid reaction mixture produces foam immediately after leaving the mixing head without the real reaction between the polyol and isocyanate components having begun. This pre-production of foam, for example comparable with shaving foam, leads to the material being dimensionally stable and remaining at the place of application.

In general, any polyurethane system having thixotropic properties that seems appropriate for the person skilled in the art can be used in step (B) of the process of the invention. According to the invention, the polyurethane system used can intrinsically have the thixotropic properties or the latter are obtained by the addition of appropriate additives.

In a preferred embodiment of the process of the invention, at least one thixotrop is added to the polyurethane system before or during step (B).

The present invention therefore preferably provides the process of the invention in which at least one thixotrop is added to the polyurethane system before or during step (B).

Appropriate thixotropes, for example, are selected from the group consisting of inorganic thixotropes, for example organometallic layered silicates, hydrophobic or hydrophilic pyrogenic silica, organic thixotropes, for example polyol esters, toluenediamide (TDA) and derivatives thereof, liquid thixotropes based on urea-urethanes, for example isophorone diamine (CAS-No.2855-13-2), 2,2'-dimethyl-4,4'-methylenebis (cyclohexylamine) (CAS-No.6664-37-5), diethyl toluene diamine (CAS-No 68479-98-1), triethylene glycol diamine (CAS-No 929-59-9), polyoxypropylenediamine (CAS-No 9046-10-0), and mixtures thereof.

The present invention therefore preferably provides the process of the invention wherein at least one thixotrop is selected from the group consisting of inorganic thixotropes, for example organo-layered silicate silicates, hydrophobic or hydrophilic pyrogenic silica, organic thixotropes, for example polyol esters, toluenediamide (TDA) and derivatives thereof, liquid thixotropes based on urea-urethanes, eg isophorone diamine (CAS-No.2855-13-2), 2,2'-dimethyl-4,4'-methylenebis (cyclohexylamine) (CAS-No 6864-37-5), diethyltoluenediamine (CAS-No 68479-98-1), triethylene glycol diamine (CAS-No 929-59-9), polyoxypropylenediamine (CAS-No.9046-10-0) , and mixtures thereof.

According to the invention, at least one thixotrop can be added to the polyurethane system or to at least one isocyanate component (a) or to at least one polyol (b), preferably to at least one isocyanate component (a) or to at least one polyol ( b) At least one thixotrope which is preferably present according to the invention, for example, is added in an amount of 0.1 to 20% by weight, preferably 0.2 to 10% by weight, particularly preferably 0.2 to 10% by weight. 7% by weight, very particularly preferably from 0.2 to 5% by weight, in each case based on at least one isocyanate component (a) or at least one polyol (b).

The polyurethane systems that can be used or are preferably used according to the invention will be described in detail below.

As the isocyanate component (a), the usual aliphatic, cycloaliphatic and in particular aromatic diliatanes and / or polyisocyanates are used. Preference is given to the use of diphenylmethane diisocyanate (MDI) and in particular mixtures of diphenylmethane diisocyanate and polyphenylenepolymethylene polyisocyanates (crude MDI). The isocyanates can also be modified, for example by the incorporation of uretdione, carbamate, isocyanurate, carbodiimide, allophanate and in particular urethane groups.

The isocyanate component (a) can also be used in the form of polyisocyanate prepolymers. These prepolymers are known from the prior art. They are prepared in a manner known per se by the reaction of polyisocyanates (a) as described above, for example at temperatures of about 80 ° C, with compounds having hydrogen atoms reactive towards isocyanates, preferably with polyols, to form polyisocyanate prepolymers. The polyol / polyisocyanate ratio is generally selected such that the NCO content of the prepolymer is from 8 to 25% by weight, preferably from 10 to 22% by weight, particularly preferably from 13 to 20% by weight.

According to the invention, particular preference is given to the use of crude MDI as isocyanate component (a).

In a preferred embodiment, the isocyanate component (a) is selected so that it has a viscosity of less than 800 mPas, preferably 100 to 650 mPas, particularly preferably from 120 to 400 mPas, in particular from 180 to 350 mPas, measured in accordance with DIN 53019 at 25 ° C.

In the polyurethane system used according to the invention, at least one polyol is preferably a mixture of polyol (b) which generally comprises polyols as a constituent (b 1), and optionally chemical blowing agents as a constituent (b 2). In general, the polyol mixture (b) comprises physical blowing agents (b3).

The viscosity of the polyol mixture (b) used according to the invention (but they are physical blowing agents (b3)) is in general from 200 to 10000 mPas, preferably from 500 to 9500 mPas, particularly preferably from 1000 to 9000 mPas , very particularly preferably from 2500 to 8500 mPas, in particular from 3100 to 8000 mPas, in each case measured in accordance with DIN 53019 at 20 ° C. In a particularly preferred embodiment, a mixture of polyol (b) (but without physical blowing agents (b3)) having a viscosity of more than 3000 mPas, for example from 3100 to 8000 mPas, in each case measured in accordance with DIN 53019 at 20 ° C, is used in the process of the invention.

The present invention therefore preferably provides the process of the invention in which a mixture of polyol (b) but without physical blowing agents (b3)) having a viscosity of more than 3000 mPas, for example from 3100 to 8000 mPas, in each case measured in accordance with DIN 53019 at 20 ° C, it is used as at least one polyol (b).

The mixture of polyol (b) in general comprises blowing agents physical (b3). However, the addition of physical blowing agent leads to a significant decrease in viscosity. It is therefore an important aspect of the invention that the viscosities of the polyol mixture (b) indicated above are related, even in the case of the polyol mixture comprising physical blowing agents, to the viscosity of the polyol mixture ( b) without the addition of physical blowing agents (b3).

Possible polyols (constituent b1) in general are compounds having at least two isocyanate-reactive groups, ie having at least two hydrogen atoms that react with the isocyanate groups. Examples thereof are compounds having OH groups, SH groups, NH groups and / or NH2 groups.

As polyols (constituent b 1), preference is given to the use of compounds based on polyesterols or polyetherols. The functionality of the polyetherols and / or polyesterols in general is from 1.9 to 8, preferably from 2.4 to 7, particularly preferably from 2.9 to 6.

The polyols (b1) have a hydroxyl number in general greater than 100 mg KOH / g, preferably greater than 150 mg KOH / g, particularly preferably greater than 200 mg KOH / g. it has generally been found that an appropriate upper limit for the number of hydroxyls is 1000 mg KOH / g, preferably 800 mg KOH / g, particularly preferably 700 mg KOH / g, very particularly preferably 600 KOH / g. The OH numbers indicated above refer to all of the polyols (b1), which does not rule out the individual constituents of the mixture that have higher values or lower.

The component (b1) preferably comprises polyether polyols are prepared by known methods, for example from one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene radical by anionic polymerization using alkali metal hydroxides such as sodium or potassium or alkoxides of alkali metal such as sodium methoxide, sodium ethoxide or potassium or isopropoxide potassium as catalysts with addition of at least one starter molecule comprising from 2 to 8, preferably 3 to 8 , reactive hydrogen atoms in linked form or by cationic polymerization using Lewis acids such as antimony pentachloride, boron fluoride etherate, etc., bleaching earth as catalysts.

Suitable alkylene oxides are, for example, tetrahydrofuran oxide, 1, 3-propylene oxide, 1, 2- or 2,3-butylene oxide, styrene oxide and preferably ethylene oxide and 1, 2-propylene. The alkylene oxides can be used individually, alternatively in succession or as mixtures.

Possible starter molecules are alcohols such as glycerol, trimethylolpropane (TMP), pentaerythritol, sugar compounds such as sucrose, sorbitol, and amines such as methylamine, ethylamine, isopropylamine, butylamine, benzylamine, aniline, toluidine, toluenediamine, naphthylamine, ethylenediamine (EDA), diethylenetriamine, 4,4-methylenedianiline, 1,3-propanediamine, 1,6-hexanediamine, ethanolamine, diethanolamine, triethanolamine and the like.

Additional initiator molecules can be used are condensation products of formaldehyde, phenol and diethanolamina or ethanolamine, formaldehyde, alqullfenoles and diethanolamine or ethanolamine, formaldehyde, bisphenol A and diethanolamine or ethanolamine, formaldehyde, aniline and diethanolamina or ethanolamine, formaldehyde, cresol and diethanolamine or ethanolamine, formaldehyde, toluidine and diethanolamine or ethanolamine and also formaldehyde, toluene diamine (TDA) and diethanolamine or ethanolamine and the like.

Preference is given to the use of glycerol, sucrose, sorbitol and EDA as starter molecule.

The polyol mixture may optionally also comprise chemical blowing agents as a constituent (b2). As chemical blowing agents, preference is given to water or carboxylic acids, in particular formic acid. The chemical blowing agent is generally used in an amount of 0.1 to 4% by weight, preferably 0.2 to 2.0% by weight and particularly preferably 0.3 to 1.5% by weight, in each case based on to the weight of component (b).

As mentioned above, the polyol blend (b) generally comprises a physical blowing agent (b3). Physical blowing agents are compounds that dissolve or emulsify in the starting materials for the production of polyurethane and vaporize under the conditions of polyurethane formation. These are, for example, hydrocarbons, for example cyclopentane, halogenated hydrocarbons and other compounds such as perfluorinated alkanes, such as perfluorohexane, chlorofluorocarbons and ethers, esters, ketones and / or acetals. They are usually used in an amount of 1 to 30% by weight, preferably 2 to 25% by weight, particularly preferably 3 to 20% by weight, based on the total weight of component (b).

The present invention therefore preferably provides the process of the invention in which the polyurethane system produces foam by means of pentane, preferably cyclopentane, as a physical blowing agent.

In a preferred embodiment, the mixture of polyol (b) comprises crosslinkers as constituent (b4). For the purposes of the present invention, the crosslinking agents are compounds having a molecular weight of 60 to 400 g / mol and having at least 3 hydrogen atoms that are reactive to isocyanates. An example is glycerol.

The crosslinking agents (b4) are generally used in an amount of 1 to 10% by weight, preferably 2 to 6% by weight, based on the total weight of the polymer mixture (b) (but without physical blowing agents (b3) )).

In another preferred embodiment, the polyol mixture (b) comprises chain extenders, which serve to increase the crosslinking density, as a constituent (b5). For the purposes of the present invention, chain extenders are compounds having a molecular weight of 60 to 400 g / mol and have 2 hydrogen atoms that are reactive to isocyanates. Examples are butanediol, diethylene glycol, dipropylene glycol and ethylene glycol.

The chain extenders (b5) are generally used in an amount of 2 to 20% by weight, preferably 4 to 15% by weight, in based on the total weight of the polyol mixture (b) (but without physical blowing agents (b3)).

The components (b4) and (b5) can be used individually or in combination in the polyol mixture.

The polyurethane foams present as insulating material according to the invention can be obtained by the reaction of the polyurethane system according to the invention.

In the reaction, at least one isocyanate component (a) and at least one polyol (b), preferably the mixture of polyol (b), are generally reacted in such amounts that the isocyanate units of the foam is 90 to 240, preferably from 90 to 200, particularly preferably from 95 to 180, very particularly preferably from 95 to 160, in particular from 100 to 149.

In a preferred embodiment, components (a) and (b) of the polyurethane system are selected so that the resulting foam has a compressive strength (at a foam density of 60 kg / m 3) greater than 0.2 N / mm2, preferably greater than 0.25 N / mm2, particularly preferably greater than 0.3 N / mm2, measured in accordance with DIN 53421.

In general, the foam density injected as a whole is more than 50 kg / m3, preferably more than 60 kg / m3, particularly preferably more than 70 kg / m3, very particularly preferably more than 80 kg / m3, in particular more than 100. kg / m3, in the process of the invention. The upper limit for the foam density injected as a whole is preferably in each case 300 kg / m3. The foam density injected as a whole is generally understood to be the total amount of liquid polyurethane material introduced based on the total volume of the annular separation for the foam.

The process of the invention can generally be carried out in any compression that seems appropriate for the person skilled in the art. For the purposes of the present invention, the compression is the total filling density of the annular gap divided by the density of the main foam in free foam determined in an uncompressed foam body.

The present invention preferably provides the process of the invention in which the reaction is carried out at a compression of less than 2.0, preferably less than 1.5, particularly preferably less than 1.4, and very particularly preferably less than 1, 3, in particular less than 1, 2.

The polyurethane system used in step (B) of the process of the invention preferably comprises at least one catalyst. According to the invention, it is generally possible to use all the catalysts that appear to be appropriate for the person skilled in the art.

The catalysts which are preferably used according to the invention catalyze the blowing reaction, ie the reaction of diisocyanate with water. This reaction takes place predominantly before the actual polyurethane chain formation, ie the polymerization reaction, and therefore leads to a reaction profile fast polyurethane system. In addition, catalysts that catalyze the polyurethane gelation reaction or the trimerization reaction of the isocyanate can preferably be used.

Examples of catalysts that can be used according to the invention are selected from the group consisting of tin organic compounds such as tin salts (II) or organic carboxylic acids, for example potassium acetate, potassium formate and / or potassium octoate, basic amine compounds such as secondary aliphatic amines, for example N, N-dimethylaminoethoxyethanol (CAS number 1704-62-7), N, N, N ' , N '-tetramethyl-2,2' Oxybis (ethylamine) (CAS number 3033-62-3), imidazoles, amidines, alkanolamines, preferably tertiary amines, for example 2 - [[2- (dimethylamino) ethyl] methylamino-ethanol (number CAS 2212-32-0), methylbis (2-dimethylaminoethyl) amine (CAS No. 3030-47-5), triethylamine, 1,4-diazabicyclo [2.2.2] octane, dimethylbenzylamine, dimethylcyclohexylamine, 2-ethylhexanoate (2-hydroxypropyl) ) trimethylammonium (CAS number 62314-22-1), N, N, N-trimethyl-2-hydroxy-1-propaneammonium format, trimethylhydroxypropyl ammonium formate, 2 - ((2-di-methylamino) ethyl) methylamino) ethanol ( CAS number 2212-32 -0) and / or N, N ', N "-tris (dimethylaminopropyl) hexahydrotriazine (CAS number 15875-13-5), glycine, monosodium salt of N - ((2-hydroxy-5-nonylphenyl) ) methyl) -N-methyl (n) CAS 56968-08-2 number) and mixtures thereof.

The catalysts which are preferred according to the invention can be added to the polyurethane system in any manner known to those skilled in the art, for example pure or as a solution, for example as an aqueous solution.

On the basis of the polyole component (b), at least one catalyst, according to the invention, is added in an amount of 0.01 to 5% by weight, preferably 0.5 to 5% by weight, particularly preferably from 1 to 5% by weight, very particularly preferably from 1.5 to 5% by weight, in particular from 2 to 5% by weight.

The additives (b6) can optionally also be added to the polyurethane system used according to the invention. For the purposes of the present invention, the additives (b6) are the usual auxiliaries and additives known in the prior art, but without physical blowing agents. Examples of surfactants, foam stabilizers, cell regulators, fillers, dyes, pigments, flame retardants, unsightly, hydrolysis inhibitors and / or bacteriostatic and fungistatic substances can be mentioned. It may be noted that the preferred and general viscosity ranges indicated above for component (b) are applied to a mixture of polyol (b) including any additive (b6) added (but excluding any physical blowing agent (b3) added) .

The present invention therefore preferably provides the process of the invention wherein at least one mixture of polyol (b) comprises polyols (b1), optionally chemical blowing agents (b2), physical blowing agents (b3), crosslinking agents ( b4), chain extenders (b5), catalysts and / or optionally additives (b6).

The present invention therefore provides, in particular, the process of the invention in which from 1 to 25% by weight of flame retardants, based on the total weight of the polyol mixture, as an additive (b6).

Stage (C): Step (C) of the process of the invention comprises producing foam and allowing curing of the polyurethane system.

The production of foam and curing, according to the invention, is generally carried out at a component temperature of 18 to 40 ° C, preferably 18 to 35 ° C, particularly preferably 22 to 30 ° C.

The production of foam and curing, according to the invention, is generally carried out at a surface temperature of 15 to 50 ° C, preferably 20 to 50 ° C, particularly preferably 25 to 45 ° C.

After step (C) of the process of the invention, an insulated tube comprising at least one middle tube, a film tube and an insulating layer composed of polyurethane foam between at least one middle tube and the film tube is obtained .

The insulating layer generally has a thickness of 1 to 20 cm, preferably 3 to 20 cm, particularly preferably 5 to 20 cm.

In another preferred embodiment, the insulating layer comprising polyurethane foam has a thermal conductivity of less than 27 mW / mK, preferably less than 26 mW / mK, particularly preferably less than 25 mW / mK, very particularly preferably less than 24 mW / mK , in particular less than 23 mW / mK, in each case measured in accordance with EN ISO 8497.

Stage (D): Step (D) of the process of the invention comprises the application of a layer of at least one material to the film tube to form the outer tube.

After step (C) of the process of the invention at least one middle tube is obtained which is surrounded by an insulating layer of at least one polyurethane foam which in turn is surrounded by the film tube produced in the stage (A ) to form the outer tube composed of at least one material, this is applied in step (D) of the process of the invention. According to the invention, in general any suitable material can be used as external tube.

In another embodiment of the process of the invention, the material from which the outer tube is formed in step (D) is a thermoplastic polymer.

The present invention therefore preferably provides the process of the invention wherein the material from which the outer tube is formed in step (D) is a thermoplastic polymer, in particular polyethylene.

The application of thermoplastic polymers, according to the invention, can be carried out by extrusion. The extrusion of the thermoplastic polymers to produce a layer, here the outer tube, is known per se to those skilled in the art.

The application according to step (D) of the process of the invention is generally carried out at a temperature that seems appropriate for the person skilled in the art for the extrusion of thermoplastic polymer, for example at the melting temperature of the thermoplastic polymer used. Suitable temperatures are, for example, 180 to 220 ° C, preferably 190 to 230 ° C or 180 to 230 ° C, preferably 190 to 220 ° C.

The external tube formed in step (D) of the process of the invention in general has a thickness of 1 to 30 mm. The internal diameter of the outer tube depends, according to the invention, on the diameter of the film tube and is, for example, 6 to 90 cm, preferably 12 to 90 cm, particularly preferably 19 to 90 cm.

The outer tube may optionally comprise a plurality of layers that may be joined during the extrusion process to produce the outer tube. An example is the introduction of multilayer films between polyurethane foam and the outer tube, the film comprising at least one metal layer to improve the barrier action. Suitable external tubes of this type are described in EP-A-960 723. This additional layer which is optionally present is preferably introduced together with the film in step (A). For example, it is possible, according to the invention, to use multilayer films comprising aluminum as a diffusion barrier.

According to the invention, all thermoplastic polymers having advantageous properties for the correspondingly insulated tube are generally suitable. Examples of thermoplastic polymers that can be used according to the invention are they are selected from the group consisting of polyethylene, polypropylene and mixtures thereof, preference being given to the use of polyethylene.

After step (D) of the process of the invention the isolated tube formed can be further treated by methods known to those skilled in the art, for example by cutting produced continuously and in principle thereby the infinitely long insulated tube in desired lengths, for example 6, 12 or 16 m.

In a particularly preferred embodiment, the insulated tube produced according to the invention is an insulated composite external tube for district heating networks placed on the floor, which complies with the requirements of DIN EN 253: 2009.

The present invention also provides an insulated tube that can be produced by the process of the invention. The details of the produced insulated tube that have been mentioned in connection with the process of the invention are applied analogously. The tube that has been produced continuously according to the invention shows a particularly uniform density distribution over the entire length and, as a result, low lambda values combined with better physical properties. At the same time, the insulated tube produced according to the invention has a large outside diameter, for example, 125 to 920 mm and / or particularly a high density of foam, for example, 50 to 300 kg / m3.

The present invention also provides an apparatus for producing an insulated tube, comprising an apparatus for introduction of at least one middle tube, an apparatus for the introduction of a film to form a film tube, a jaw band, an apparatus for forming an outer tube and an apparatus for the addition of at least one thixotrop, preferably to carry the process of the invention. An apparatus for introducing at least one thixotrop is, for example, a multi-component mixing head or introduction through a static mixer into the high pressure circuit.

According to the invention, at least one thixotrop, as described above, can be added during or shortly before the production of the polyurethane foam. In a second embodiment according to the invention, at least one thixotrop is mixed generating at least one of the precursor compounds for the production thereof and is brought to the location where the polyurethane foam is produced and mixed there with the other compounds precursors.

The individual apparatuses described are known per se to those skilled in the art. In the case of the apparatus of the invention, preferably to carry out the process of the invention, these apparatuses known per se have to be arranged according to the invention.

The present invention also provides the use of the apparatus of the invention to carry out the process of the invention, in particular to produce the insulated tube according to the invention.

Claims

1. A continuous process for producing an insulated tube comprising at least one middle tube, an outer tube, a layer of at least one polyurethane between at least one middle tube and outer tube and a film tube between at least one polyurethane and the outer tube , which comprises at least the stages: (A) Provision, in a jaw band, of at least one middle tube and one tube of film formed continuously from a film, wherein at least one middle tube is disposed within the tube of film in such a way that it is forms a separation between at least one middle tube and the film tube, (B) introduction of a polyurethane system comprising at least one isocyanate component (a) and at least one polyol (b) in the separation, (C) produce foam and allow the curing of the polyurethane system and (D) application of a layer of at least one material to the film tube to form the outer tube, wherein the polyurethane system has thixotropic properties, and at least one thixotrop is added to the polyurethane system before or during step (B).

2. The process according to claim 1, wherein at least one thixotrop is selected from the group consisting of thixotropes inorganic, for example organometallic layered silicates, hydrophobic or hydrophilic pyrogenic silica, organic thixotropes, for example polyol esters, toluenediamide (TDA) and derivatives thereof, liquid thixotropes based on urea-urethanes, for example isophoronadiamine (CAS-No. 2855-13-2), 2,2'-dimethyl-4,4'-methylenebis (cyclohexylamine) (CAS-No.6664-37-5), diethyltoluenediamine (CAS-No 68479-98-1), triethylene glycolamine (CAS No. 929-59-9), polyoxypropylenediamine (CAS-No, 9046-10-0), and mixtures thereof.

3. The process according to claim 1 or 2, wherein the material from which the outer tube is formed in step (D) is a thermoplastic polymer.

4. The process according to any one of claims 1 to 3, wherein the film used has a width that allows a corresponding film tube to be formed having an internal diameter of 6 to 90 cm, preferably 12 to 90 cm, particularly preferably from 19 to 90 cm, very particularly preferably from 35 to 90 cm.

5. The process according to any one of claims 1 to 4, wherein the foam density injected as a whole is more than 50 kg / m3, preferably more than 60 kg / m3, particularly preferably more than 70 kg / m3, very particularly preferably more than 80 kg / m3, in particular more than 100 kg / m3.

6. An insulated tube that can be produced by the process according to any one of claims 1 to 5.

7. An apparatus for producing an insulated tube, comprising an apparatus for introducing at least one medium tube, an apparatus for introducing a film to form a film tube, a jaw band, an apparatus for forming an outer tube and an apparatus for the addition of at least one thixotropic.

8. The use of the apparatus according to claim 7 to carry out the process according to any one of claims 1 to 5.

9. The use according to claim 8 for producing the insulated tube according to claim 6.